Non-volatile data storage devices have enabled increased portability of data and software applications. As research and development in the field of data storage devices progresses, data storage devices are able to store increasingly larger amounts of data. A data storage device may be used as “embedded” memory of a portable computing device (e.g., mobile phone). The data storage device may be mounted to a circuit board of the portable computing device using reflow soldering. Prior to the reflow soldering, certain data may have been stored in the data storage device using a preloading process. In some situations, one or more blocks within the data storage device may be partially written (e.g., because the total amount of data written to the data storage device is not divisible by the block size of the data storage device). The partially written block(s) may include programmed word lines as well as unprogrammed word lines. Due to effects of heating caused by the reflow process, the unprogrammed word lines may exhibit poor data retention and threshold voltage shifting, as compared to other word lines. Thus, certain portions of the data storage device may have lower reliability than other portions of the data storage device.